Search results for " solution"
showing 10 items of 3084 documents
First principles calculations of (Ba,Sr)(Co,Fe)O3−δ structural stability
2013
Abstract First principles total-energy calculations of an ideal BSCF perovskite-type solid solution, the crystal containing basic point defects, and a set of relevant solid–solid solutions are presented. Our DFT modeling of defects (Frenkel, Schottky and cation exchange) and disordering in the BSCF perovskites reveals that the material tends to decompose at relatively low temperatures into a mixture of new perovskite and oxide phases. These new phases are likely to appear at grain boundaries and surface interfaces. This instability is predicted to negate advantages of fast oxygen transport chemistry and impede the applicability of BSCF-based SOFC and ceramic permeation membranes. We discuss…
Electrochemical impedance spectroscopy for studying passive layers on steel rebars immersed in alkaline solutions simulating concrete pores
2007
Present paper deals with the use of the electrochemical impedance spectroscopy to identify different processes in the passive layer growth over steel rebar surface immersed in an alkaline media simulating the concrete pore solution. Two cases have been considered: a passive layer spontaneously grown in a high alkaline media and a passive layer assisted by the application of an anodic potential in the same media. The application of electric equivalent circuits allows distinguishing between the different mechanisms occurring in this passive layer when grows in different conditions. An electric equivalent circuit with two RC loops connected in parallel is often used for fitting the EIS diagram…
Dielectric nonlinearity of ferroelectric solid solutions PMN-PZN and PMN-PNN
2001
Abstract Obtaining of novel thin film materials for electrically tuneable capacities is one of the current problems of ferroelectric material application. The most appropriate materials are the ferroelectric lead-containing niobates: PbMg1/3Nb2/3O3 (PMN), PhZn1/3Nb2/3Os (PZN), PbNi1/3Nb2/3O3 (PNN) and their solid solutions were synthesized by solid state reactions at 800–900 °C from oxides. Results of the studies of thermal dependence of dielectric permeability and loss factors of the synthesized solutions are provided together with reciprocal dielectric permeability as function of temperature and electric field intensity. The dielectric characteristics of nonlinear materials are reported e…
<title>Raman scattering by phonons and magnons in Ni<formula><inf><roman>c</roman></inf></formula>Mg<for…
2003
ABSTRACT The Raman scattering by phonons and magnons was studied at room temperature in polycrystalline solid solutions NiMg1O and pure NiO. The experimental Raman spectrum of NiO consists of six well resolved bands, whose originis due to the disorder-induced one-phonon scattering (bands at 400 and 500 cm'), two-phonon scattering (bands at 750,900 and 1 100 cm) and two-magnon scattering (band at 1500 cm). In NiMg1O solid solutions, a relative increase ofone-phonon scattering is observed upon a dilution of nickel oxide by magnesium ions: at room temperature, the two-magnon band becomes invisible for c<O.7, whereas the two-phonon contribution disappears at c<O.5. Such behaviour isexplained by…
Femtosecond laser fragmentation from water-dispersed microcolloids: toward fast controllable growth of ultrapure Si-based nanomaterials for biologica…
2020
International audience; An ultrashort laser-assisted method for fast production of concentrated aqueous solutions of ultrapure Si-based colloidal nanoparticles is reported. The method profits from the 3D geometry of femtosecond laser ablation of water-dispersed microscale colloids, prepared preliminarily by the mechanical milling of a Si wafer, in order to avoid strong concentration gradients in the ablated material and provide similar conditions of nanocluster growth within a relatively large laser caustics volume. We demonstrate the possibility for the fast synthesis of non-aggregated, low-size-dispersed, crystalline Si-based nanoparticles, whose size and surface oxidation can be controll…
Electronic excitations in ZnWO4 and ZnxNi1−x WO4 (x = 0.1 − 0.9) using VUV synchrotron radiation
2011
The photoluminescence spectra and luminescence excitation spectra of pure microcrystalline and nano-sized ZnWO4 as well as the Zn x Ni1−x WO4 solid solutions were studied using vacuum ultraviolet (VUV) synchrotron radiation. The samples were also characterized by x-ray powder diffraction. We found that: (i) the shape of the photoluminescence band at 2.5 eV, being due to radiative electron transitions within the [WO6]6− anions, becomes modulated by the optical absorption of Ni2+ ions in the Zn x Ni1−x WO4 solid solutions; and (ii) no significant change in the excitation spectra of Zn0.9Ni0.1WO4 is observed compared to pure ZnWO4. At the same time, a shift of the excitonic bands to smaller en…
X-ray absorption and Raman spectroscopy studies of tungstates solid solutions ZncNi1-cWO4 (c=0.0-1.0)
2020
G.B. acknowledges the financial support provided by the State Education Development Agency for project No. 1.1.1.2/VIAA/3/19/444 (agreement No. 1.1.1.2/16/I/001) realized at the Institute of Solid State Physics, University of Latvia. A.K. and A.K. would like to thank the support of the Latvian Council of Science project No. lzp-2019/1-0071. Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the European Union’s Horizon 2020 Framework Programme H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2.
The role of molecular oxygen in the formation of radiation-engineered multifunctional nanogels
2019
Abstract Nanogels are very promising biomedical nanodevices. The classic “radiation chemistry-based” approach to synthetize nanogels consists in the irradiation with pulsed electron beams of dilute, N2O-saturated, aqueous solutions of water-soluble polymers of the “crosslinking type”. Nanogels with controlled size and properties are produced in a single irradiation step with no recourse to initiators, organic solvents and surfactants. This paper combines experimental syntheses, performed with two e-beam irradiation setups and dose-ranges, starting from poly(N-vinyl pyrrolidone) solutions of various concentrations, both in N2O-saturated and air-saturated initial conditions, with the numerica…
Phase behaviour and interfacial tension of polysiloxane blends
1998
Abstract The cloud point curve for blends of poly(dimethyisiloxane) (PDMS, M w = 2.5kg mol −1 ) and poly(hexylmethylsiloxane) (PHMS, M w = 113kg mol − ] was determined turbidimetrically. The system demixes upon cooling and the UCST amounts to 36°C. The interfacial tension γ was determined at the critical composition for three temperatures by means of a spinning drop tensiometer. The dependence of γ on the reduced critical temperature can be described within experimental error by both the mean field theory and the Ising-3D theory.
Thermodynamics of Phase Behavior in PEO/P(EO-b-DMS) Homopolymer and Block Co-Oligomer Mixtures under Pressure
2003
The cloud-point temperatures (T-cl's) of poly(ethylene oxide) (PEO) and poly(ethylene oxide)-block-polydimethylsiloxane (P(EO-b-DMS)) homopolymer and block-oligomer mixtures were determined by turbidity measurements over a range of temperatures (105 to 130degrees), pressures (1 to 800 bar), and compositions (10-40 wt.-% PEO). The system phase separates upon cooling and T-cl was found to decrease with an increase in pressure for a constant composition. In the absence of special effects, this finding indicates negative excess volumes. Special attention was paid to the demixing temperatures as a function of the pressure for the different polymer mixtures and the plots in the T-phi plane (where…